A movement distance detector which is simple in structure, low-cost and highly accurate. The detector includes a magnet movable along a path, a magnetic body arranged along the path, and a magnetically sensitive element attached to one end of the magnetic body. When the magnet is moved along the path, a magnetic circuit is formed by the oppositely arranged magnet and magnetic body. The number of magnetic fluxes focused by the magnetic body changes with the movement distance of the magnet. The magnetically sensitive element detects the change in number of magnetic fluxes, that is, the movement distance. The magnetic body may be a rod, a truncated pyramid or a cylinder.